The present invention relates generally to a drilling machine, and more particularly to a drilling machine which has a number of tools therein. The drilling machine automatically selects a desired tool and functions like a so-called drilling machine with an automatic tool changer (A.T.C.).
A drilling machine with an automatic tool changer is basically comprised of: a bed; a table which is slidably located on the bed and moves a workpiece to any desired position along a horizontal plane; a tool which is arranged vertically and drills the work; a spindle, to which the tool is detachably connected, which rotates together with the tool; a spindle head by which the spindle is rotatably held; a spindle driving motor which is mounted to the spindle head and rotates the spindle; a lead screw, which is fixed to the bed, and located near the spindle head, and is extended parallel to the spindle; a ball nut which is provided in the spindle head and engaged with the lead screw;
A driving motor which rotates said lead screw and moves said spindle head, together with the said spindle and said spindle driving motor, by means of said ball nut provided in the spindle head. In the above described drilling machine with an automatic tool changer, the tool is one of a predetermined number of tools. These tools are rotatably held by a circular tool magazine and are arranged at a constant pitch along the periphery thereof. Furthermore, the circular tool magazine is rotatable with respect to the spindle head in an intermittent motion. Each of the tools comes under the spindle when the circular tool magazine rotates in an intermittent motion. When one of the tools is needed for drilling, the spindle head is traversed upward by the driving motor, together with the spindle and also with the spindle driving motor, by means of the lead screw and the ball nut. Then, the tool magazine can freely rotate without running against the spindle. Subsequently, the desired tool comes under the spindle and the axis of the desired tool is aligned with the axis of the spindle. After this, the spindle head is traversed downwardly, thereby connecting the spindle with the desired tool.
In the drilling machine with an automatic tool changer of the prior art, the circular tool magazine is rotated by an electric pulse motor. As a result of the electric pulse motor being provided inside the circular tool magazine, the circular tool magazine is of a relatively large size, heavy weight and complicated construction. Further, the cost of the circular tool magazine becomes relatively high. This is because the circular tool magazine requires an electric pulse motor which only drives the circular tool magazine and a drive control circuit which only controls the electric pulse motor.
Therefore, it is the principal object of the present invention to provide a drilling machine with an automatic tool changer consisting of a circular tool magazine which requires no driving motor mechanism such as an electric pulse motor inside or outside of the circular tool magazine. Accordingly, the drilling machine with an automatic tool changer of the present invention is of a relatively small size, light weight, simple in construction and low in cost.